#include <iostream>

using namespace std;


int sum(int x, int y = m + n, int z = m * n);

int m = 15, n = 28;

int main() {

    int x(5), y(8);
    int s1 = sum(x);
    int s2 = sum(x, y);
    cout << "s1=" << s1 << "\n" << "s2=" << s2 << endl;
    return 0;
}

int sum(int x, int y, int z) {
    return x + y + z;
}
